Person: BEĞEN, Ali Cengiz
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Ali Cengiz
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BEĞEN
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ArticlePublication Metadata only Enhancing MPEG DASH performance via server and network assistance(IEEE, 2017) Thomas, E.; Deventer, M.O. van; Stockhammer, T.; Beğen, Ali Cengiz; Famaey, J.; Computer Science; BEĞEN, Ali CengizMPEG-Dynamic Adaptive Streaming over HTTP (DASH) provides formats that are suitable to stream media content over HTTP. Typically, the DASH client adaptively requests small chunks of media based on the available bandwidth and other resources. This client-pull technology has proven to be more flexible, firewall-friendly, and CDN-scalable than server-push technologies. However, service providers have less control given the decentralized and client-driven nature of DASH, which introduces new challenges for them to offer a consistent and possibly higher quality of service for premium users. MPEG addresses this issue in a new work referred to as Server and Network-assisted DASH (SAND). The key features of SAND are asynchronous network-to-client and network-to-network communication, and the exchange of quality-related assisting information in such a way that it does not delay or interfere with the delivery of the streaming media content. MPEG has completed the work on SAND first edition and will be published as a new part of the MPEG-DASH standard by early 2017.ArticlePublication Metadata only A survey on bitrate adaptation schemes for streaming media over HTTP(IEEE, 2019) Bentaleb, A.; Taani, B.; Beğen, Ali Cengiz; Timmerer, C.; Zimmermann, R.; Computer Science; BEĞEN, Ali CengizIn this survey, we present state-of-the-art bitrate adaptation algorithms for HTTP adaptive streaming (HAS). As a key distinction from other streaming approaches, the bitrate adaptation algorithms in HAS are chiefly executed at each client, i.e., in a distributed manner. The objective of these algorithms is to ensure a high quality of experience (QoE) for viewers in the presence of bandwidth fluctuations due to factors like signal strength, network congestion, network reconvergence events, etc. While such fluctuations are common in public Internet, they can also occur in home networksor even managed networks where there is often admission control and QoS tools. Bitrate adaptation algorithms may take factors like bandwidth estimations, playback buffer fullness, device features, viewer preferences, and content features into account, albeit with different weights. Since the viewer's QoE needs to be determined in real-time during playback, objective metrics are generally used including number of buffer stalls, duration of startup delay, frequency and amount of quality oscillations, and video instability. By design, the standards for HAS do not mandate any particular adaptation algorithm, leaving it to system builders to innovate and implement their own method. This survey provides an overview of the different methods proposed over the last several years.ArticlePublication Metadata only Consumer communications and the next generation broadcast networks(IEEE, 2016) Beğen, Ali Cengiz; Kolberg, M.; Merabti, M.; Computer Science; BEĞEN, Ali CengizOver 20 years ago the challenge for the communications community was the convergence between networking, telecommunication, and broadcasting. This challenge has been fairly well met, and we now note that around the world telco companies are being re-born as new hybrid telco-broadcast entities, and the reverse is true for many broadcasting corporations that provide Internet services in addition to their core business. Current and new infrastructure networks now face a number of major challenges that include increasing efficiency in the delivery of services from the installed or legacy systems, and an evolution path to address more topical concerns such as energy conservation and the increased heterogeneity in media, applications, and delivery systems. Central to all of these are the ever changing consumer communication habits and demands. These particular themes are addressed in this issue.ArticlePublication Metadata only QoE-aware bandwidth broker for HTTP adaptive streaming flows in an SDN-enabled HFC network(IEEE, 2018-06) Bentaleb, A.; Beğen, Ali Cengiz; Zimmermann, R.; Computer Science; BEĞEN, Ali CengizThis paper proposes a software defined networking based bandwidth broker solution for improving viewer experience for any type of content delivered to any type of consumer device using HTTP adaptive streaming (HAS) in a hybrid fiber coax network. This solution is designed to meet per-session and per-group quality-of-experience objectives, to avoid common HAS culprits such as video instability, unfair and unequal quality distribution and network resource underutilization, and to scale to a large number of concurrent HAS sessions without introducing too much overhead. The mathematical framework behind our solution solves a convex optimization problem, which relies on a concave network utility maximization function. Results confirm the effectiveness of the proposed solution over the state-of-the-art bitrate adaptation and bandwidth allocation schemes.ArticlePublication Open Access Catching the moment with LoL + in twitch-like low-latency live streaming platforms(IEEE, 2022) Bentaleb, A.; Akçay, Mehmet Necmettin; Lim, M.; Beğen, Ali Cengiz; Zimmermann, R.; Computer Science; BEĞEN, Ali Cengiz; Akçay, Mehmet NecmettinOur earlier Low-on-Latency (dubbed as LoL) solution offered an accurate bandwidth prediction and rate adaptation algorithm tailored for live streaming applications that targeted an end-to-end latency of up to two seconds. While LoL was a significant step forward in multi-bitrate low-latency live streaming, further experimentation and testing showed that there was room for improvement in three areas. First, LoL used hard-coded parameters computed from an offline training process in the rate adaptation algorithm and this was seen as a significant barrier in LoL's wide deployment. Second, LoL's objective was to maximize a collective QoE function. Yet, certain use cases have specific objectives besides the singular QoE and this had to be accommodated. Third, the adaptive playback speed control failed to produce satisfying results in some scenarios. Our goal in this paper is to address these areas and make LoL sufficiently robust to deploy. We refer to the enhanced solution as LoL+ which has been integrated to the official dash.js player in v3.2.0.ArticlePublication Metadata only Performance analysis of ACTE: A bandwidth prediction method for low-latency chunked streaming(Association for Computing Machinery, Inc, 2020-07) Bentaleb, A.; Timmerer, C.; Beğen, Ali Cengiz; Zimmermann, R.; Computer Science; BEĞEN, Ali CengizHTTP adaptive streaming with chunked transfer encoding can offer low-latency streaming without sacrificing the coding efficiency. This allows media segments to be delivered while still being packaged. However, conventional schemes often make widely inaccurate bandwidth measurements due to the presence of idle periods between the chunks and hence this is causing sub-optimal adaptation decisions. To address this issue, we earlier proposed ACTE (ABR for Chunked Transfer Encoding) [6], a bandwidth prediction scheme for low-latency chunked streaming. While ACTE was a significant step forward, in this study we focus on two still remaining open areas, namely, (i) quantifying the impact of encoding parameters, including chunk and segment durations, bitrate levels, minimum interval between IDR-frames and frame rate on ACTE, and (ii) exploring the impact of video content complexity on ACTE. We thoroughly investigate these questions and report on our findings. We also discuss some additional issues that arise in the context of pursuing very low latency HTTP video streaming.ArticlePublication Metadata only Game of streaming players: Is consensus viable or an illusion?(Association for Computing Machinery, Inc, 2019-08) Bentaleb, A.; Beğen, Ali Cengiz; Harous, S.; Zimmermann, R.; Computer Science; BEĞEN, Ali CengizThe dramatic growth of HTTP adaptive streaming (HAS) traffic represents a practical challenge for service providers in satisfying the demand from their customers. Achieving this in a network where multiple players share the network capacity has so far proved hard because of the bandwidth competition among the HAS players. This competition is exacerbated by the bandwidth overestimation that is introduced due to the isolated and selfish behavior of the HAS players. Each player strives individually to select the maximum bitrate without considering the co-existing players or network resource dynamics. As a result, the HAS players suffer from video quality instability, quality unfairness, and network underutilization or oversubscription, and the players observe a poor quality of experience (QoE). To address this issue, we propose a fully distributed game theory and consensus-based collaborative adaptive bitrate solution for shared network environments, termed Game Theory and consensus-based Approach for Cooperative HAS delivery systems (GTAC). Our solution consists of two-stage games that run in parallel during a streaming session. We extensively evaluate GTAC on a broad set of trace-driven and real-world experiments. Results show that GTAC enhances the viewer QoE by up to 22%, presentation quality stability by up to 24%, fairness by at least 31%, and network utilization by 28% compared to the well-known schemes.ArticlePublication Metadata only Game of protocols: Is QUIC ready for prime time streaming?(Wiley, 2020-05) Arısu, Şevket; Yıldız, Ertan; Beğen, Ali Cengiz; Computer Science; BEĞEN, Ali Cengiz; Arısu, Şevket; Yıldız, ErtanQuick User Datagram Protocol (UDP) Internet Connections (QUIC) is an experimental and low-latency transport protocol proposed by Google, which is still being improved and specified in the Internet Engineering Task Force (IETF). The viewer's quality of experience (QoE) in HTTP adaptive streaming (HAS) applications may be improved with the help of QUIC's low-latency, improved congestion control, and multiplexing features. We measured the streaming performance of QUIC on wireless and cellular networks in order to understand whether the problems that occur when running HTTP over TCP can be reduced by using HTTP over QUIC. The performance of QUIC was tested in the presence of network interface changes caused by the mobility of the viewer. We observed that QUIC resulted in quicker start of media streams, better streaming, and seeking experience, especially during the higher levels of congestion in the network and had a better performance than TCP when the viewer was mobile and switched between the wireless networks. Furthermore, we measured QUIC's performance in an emulated network that had a various amount of losses and delays to evaluate how QUIC's multiplexing feature would be beneficial for HAS applications. We compared the performance of HAS applications using multiplexing video streams with HTTP/1.1 over multiple TCP connections to HTTP/2 over one TCP connection and to QUIC over one UDP connection. To that effect, we observed that QUIC provided better performance than TCP on a network that had large delays. However, QUIC did not provide a significant improvement when the loss rate was large. Finally, we analyzed the performance of the congestion control mechanisms implemented by QUIC and TCP, and tested their ability to provide fairness among streaming clients. We found that QUIC always provided fairness among QUIC flows, but was not always fair to TCP.Conference ObjectPublication Open Access Dynamic CDN switching - dash-if content steering in dash.js(ACM, 2023-06-16) Silhavy, D.; Law, W.; Pham, S.; Beğen, Ali Cengiz; Giladi, A.; Balk, A.; Computer Science; BEĞEN, Ali CengizThis paper overviews the content steering specification currently being developed in DASH Industry Forum and first implemented in the dash.js reference player.Conference ObjectPublication Metadata only Rate-adaptive streaming of 360-degree videos with head-motion-aware viewport margins(IEEE, 2022) Akçay, Mehmet Necmettin; Kara, Burak; Beğen, Ali Cengiz; Ahsan, S.; Curcio, I. D. D.; Aksu, E.; Computer Science; BEĞEN, Ali Cengiz; Akçay, Mehmet Necmettin; Kara, BurakEfficient use of available bandwidth is vital when streaming 360-degree videos as users rarely have enough bandwidth for a pleasant experience. A promising solution is the combination of viewport-dependent streaming using tiled video and rate adaptation, where the goal is to spend most of the available bandwidth for the viewport tiles. However, head motions resulting in a change in the viewport tiles briefly cause low-quality rendering until the new tiles can be replaced with high-quality versions. Previously, viewport margins-fixed regions around the viewport rendered at a medium quality-were proposed to make the viewport changes less abrupt. Later on, Head-motion-aware Viewport Margins (HMAVM) were implemented to further smooth the transitions at the expense of increased bandwidth consumption. In this paper, we manage the overall bandwidth cost of HMAVMs better by first developing a set of algorithms that trade off the quality of some viewport tiles and then making the margin selection part of the rate-adaptation algorithm.